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Stem cell research is one of the most promising areas of current medical research. Embryonic stem cells (ESCs) have shown an ability to mature into almost any kind of adult cell, be it neuronal, muscle, cardiac, or anything else required. This unprecedented ability has potential applications in the treatment of myriad diseases and conditions, including some of the most common and devastating: Parkinson’s, Alzheimer’s, Type I diabetes, and spinal cord injuries to name just a few.
The problem with ESCs, though, has always been the “E”— embryonic. The stem cell lines used for research have all come from human embryos left over from fertility treatments. The use of embryos for this purpose has caused a great deal of moral debate, and in reaction to these concerns the US and several other governments have placed some stringent limitations on stem cell research. Additionally, all stem cells used for research in the US are derived from only twenty-two couples who are middle-class, mostly white, and infertile. Research from cells with such limited diversity may not be universally applicable.
The end of these problems may be in sight. Within the last two months, three different sets of researchers have announced new sources of stem cells which may have sufficient properties in common with ESCs to allow for stem cell research to proceed unhindered. Two of the groups have independently come up with the same alternative source for a working stem cell replacement— testicles. The third has come up with something completely different.
In March of 2006, Gerd Hassenfuss and a team of researchers from Georg-Auguste University in Gottingen, Germany published a paper in the journal Nature. In it they detail the development of what they call “multipotent adult germline stem cells” (maGSCs). Working from spermatogonial (sperm-producing) cells obtained from the testicles of adult mice, the German team has successfully produced several lines of cells that mimic the abilities of ESCs. They can survive in culture, and they can be coaxed into becoming virtually any kind of mature tissue, a trait known as pluripotency. Most importantly, since they derive from an adult source, the ethical issues surrounding embryonic cultures become irrelevant.
The German team is already beginning to expand their research to human spermatogonial cells, using volunteers already undergoing testicular biopsies as part of IVF treatment. Given their achievement with the mouse cells, they are confident of their eventual success.
While the German team may have been the first to publish, they may actually be a little late on the research. Some four months earlier, a California company by the name of PrimeGen Biotech LLC announced a proprietary method for deriving what they called PrimeCells from human spermatogonial cells. By their description, PrimeCells are essentially the same as the Germans’ maGSCs. PrimeCells are culturable, and PrimeGen states that they have successfully derived heart, brain, bone, and cartilage from their human-source PrimeCells, placing them at least one large step ahead of the Germans. One important difference— since PrimeGen is a company rather than a university, their proprietary methods are unlikely to be published free for the taking. Until the German team catches up, other researchers will likely have to apply to PrimeGen if they want to do stem cell research using spermatogonially derived cells.
Almost simultaneously with the Nature article came a news release about stem cells from a completely different source. This one promises to be much easier to work with, requiring little more than growth medium, rather than the special treatments of the spermatogonial tissue. Dr. Shunichiro Miyoshi of Keio University announced that he and his colleagues had successfully harvested stem cells from the menstrual blood of six women. The researchers have successfully derived heart cells from the collected stem cells, but their potential for pluripotency has not been assessed. Historically other adult stem cells— such as those derived from bone marrow— have not been pluripotent, so this a distinct concern.
Another difference between the two sources is the probable effects of cellular aging. The stem cells harvested from menstrual tissue are likely affected by normal aging. The researchers warn that harvesting is likely to be more useful in younger women, because as the woman ages her cells do as well. Reproductive cells, or Germ cells, may be exempt from this process— the cellular clock must be reset at some point so that offspring can benefit, but exactly how this works is still unknown. This is the reason PrimeGen lists for researching the harvesting of female germ cells, despite the probable difficulties they will encounter. Theoretically, cells derived from female germ cells should have similar or identical properties to those derived from male spermatogonial cells.
Both of these new sources promise much for the future of stem cell research. If the entire human race suddenly becomes a potential source for cells, then the genetic limitations of the twenty-two US-legal ESC lines is no longer a problem. If non-lethal adult sources for these cells are available, then the ethical issues surrounding cell lines vanish. In short, if PrimeCells and maGSCs prove to be what their creators claim, or if the menstrually collected stem cells prove pluripotent, biology and medicine could be truly revolutionized.